Alcohol consumption is associated with a lower incidence of rheumatoid arthritis (RA), partially explained by its effects on the innate and adaptative immune system, but smoking coupled with increased alcohol consumption may attenuate the potential protective effect of alcohol intake on RA incidence, study findings published in RMD Open suggest.
This analysis of the prospective Swedish National March Cohort study featured 41,068 participants who provided smoking and alcohol data at baseline in 1997. During a mean follow-up period of 17.7 years, the investigators identified 577 incident cases of RA through linkage to multiple nationwide and complete registers.
Researchers evaluated the association between alcohol intake and RA incidence in multivariate Cox proportional hazards models. The additive effect of smoking on alcohol consumption was also evaluated in relationship to RA incidence.
Average age at RA diagnosis was 66.8 years across the 577 participants with incident RA. Among these participants, the investigators found an association between alcohol consumption and a 30% reduction in RA incidence (hazard ratio [HR], 0.69; 95% CI, 0.55-0.86). Overall, there was a significant inverse dose-response relationship between weekly alcohol consumption amount and the incidence of RA (P <.001). No significant difference was observed between participants who consumed wine exclusively (HR, 0.66; 95% CI, 0.45-0.96) vs those who drank other alcoholic beverages (HR, 0.69; 95% CI, 0.56-0.86).
Smoking among people who didn’t drink alcohol was associated with an increased incidence of RA (HR, 2.80; 95% CI, 1.96-4.01), but the effect of smoking on RA incidence was smaller in people who did drink alcohol (HR, 1.45; 95% CI, 1.21-1.74). The investigators observed an overall synergistic effect between alcohol consumption and smoking (attributable percentage due to interaction, 0.40; 95% CI, 0.15-0.64). According to the researchers, this finding suggests that 40% of the RA cases among people who smoke and drink are intrinsically attributed to the interaction.
Possible limitations of this study include the low number of current smokers at baseline as well as the reliance on self-reported data for alcohol consumption and smoking habits.
The investigators noted that additional research is required “to understand the mechanisms behind the findings which may contribute to define ways to achieve protection against RA by other means than alcohol consumption.”
Hedenstierna L, Bellocco R, Ye W, et al. Effects of alcohol consumption and smoking on risk for RA: results from a Swedish prospective cohort study. RMD Open. 2021;7(1):e001379. doi:10.1136/rmdopen-2020-001379